Time to Plan Winegrape Pest Control

Napa Valley Grapegrowers share strategies to fight damaging bugs

by Paul Franson
vineyard EGVM LBAM
Dr. Kent Daane of UC Berkeley discussed the current trifecta of vineyard pests: the European grapevine moth, vine mealybug and the light brown apple moth.
Napa, Calif.Napa Valley Grapegrowers continued its series of educational programs about sustainable vineyard practices for vineyard owners and managers March 30 with intense discussions about “Seasonal Pest & Disease Management Programs.”

It was the first part of several sessions and featured current research and new progressive approaches, starting with advances in mating disruption of European grapevine moth, vine mealybug and light brown apple moth presented by Dr. Kent Daane, University of California, Berkeley.

Representatives of Pacific Biocontrol Corp., supplier of Isomate, and Suterra, which makes Checkmate, explained costs, application, timing and new developments of these mating-disruption products.

Finally, three growers presented a panel discussion detailing their seasonal approaches to pest management and spray programs.

Daane, a well-known entomologist with the Kearney Parlier Ag Center of UC Berkeley, noted that when faced with a new pest, growers and authorities first must decide whether eradication is possible. If not, is suppression practical?

He mentioned that attempts to eradicate pests haven’t been particularly successful, and reminded the audience of the California invasion of Mediterranean fruit fly (medfly) in the mid-1980s. The state fought it with widespread aerial spraying of toxic Malathion, which would not be acceptable now.

Daane asked, “What if eradication works? How do we prevent re-infestation?” He said some pests are now so widespread that they probably can’t be eradicated, but said they might still be reduced to levels that are less damaging.

He suggested the light brown apple moth as such a pest and questioned whether it’s as serious a threat as it was originally considered. “They have it in Australia but don’t generally spray for it. And we don’t spray for some pests.”

He added, “It’s likely here to stay, but we’ve found that it has many native predators that may keep it in control.”

Get down on vine mealybug

European grapevine moth, he said, is a more direct threat—but easier to eradicate. Vine mealybug, on the other hand, can be controlled with sustainable methods. Daane suggested that, with abundant natural predators, the native grape mealybug may not require spraying. He added that the long-tailed mealybug can’t live outside a coastal climate, but the spotted Gill’s mealybug demands immediate spraying.

Vine mealybug is the greatest concern. “It causes more damage. It can spread leafroll virus. It has more generations per season and more eggs per female (than related species). And it drips honeydew on grape clusters.”

Daane observed that insecticides work best on small bugs. Older vines with lots of bark and hollow centers are harder to spray effectively, and vigorous vines are more impacted by vine mealybug. Systemic insecticides like Movento are effective against them; he recommended Lorspan for really tough situations.

Timing can be critical when applying Movento. For winegrapes in coastal regions, May and June seem best. “You may have to follow up with foliar sprays,” he added. “You want the mealybugs exposed.”

He said that April is the best time to spray with Applaud, which may require two applications two to three weeks apart. “Applaud works well in older generations,” according to Daane.

For soil application, choices include Clutch, Admire, Platinum, Movento and Applaud. Daane said Clutch works better as a foliar spray, but some growers don’t like spraying when tourists are around. Post-harvest, Lorspan is effective; Movento and Sevin also give excellent results.

He added, “If you don’t have vine mealybugs, continue to monitor with traps, starting in July. Signs of infestation include ants on trunks, wet-looking trunks in August and early dropped leaves.

Daane recommended Movento, Admire or other systemic insecticide for light infestations. Follow by spraying with Applaud. For moderate to heavy infestations, spray with Lorspan—although it also kills beneficials.

Mating disruption is effective—but not alone. “Followed by two applications of Applaud, it got the numbers way down,” he reported.

He warned that it can take three years for mating disruption to achieve substantial results, but it does prevent spreading. It lets you spray or release parasites in already impacted areas. It isn’t effective in heavily infested areas. “Mating disruption can work, but it’s just one tool,” Daane noted.

Scientists are researching many natural predators for the bugs, but are cautious about introducing new problems.

Daane summarized: If you have moderate infestations of vine mealybug, use mating disruption, annual applications of Movento and follow up with Applaud or Clutch. Consider parasitic controls.

He added, though, “If you have a severe problem, you can’t be sustainable. You have to use a chemical insecticide.”

For more information on the talks, visit napagrowers.org or call the Napa Valley Grapegrowers at (707) 944-8311.

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